The type of artificial turf made for sports has changed drastically over the last five years. The old brush type turf was glued to a shock pad that, in turn, was glued to an asphalt or concrete base. The new type of turf is installed over a packed base of crushed limestone, granite dust, crushed rocks, or stabilized soil. The turf face is then infilled with a recycled ground rubber, virgin rubber, sand or a combination of particles to hold the turf in place. The infilled particles act as a ballast and add cushion at the same time. These types of products do not need to be glued down.
However, rain has a tendency to wash away the rubber particles in the infill. This is especially true if the field is installed with a grade that peaks in the center of the field. When the particles wash away, the particulate cushion is depleted and less uniform. Eventually, the field becomes hard and inconsistent. Even the best particulate infills erode and/or compact over time. Rain and frequent use not only wash the particles away, but also press the remaining particles together, making the field harder. Eventually the field becomes so hard that it must be replaced.
The standard for measuring the hardness (impact resistance) of artificial turf is astm f 355 (“the g-max test”). The harder the field, the higher the g-max value. According to the U.S. Consumer Product Safety Commission, an artificial field should not exceed a g-max value of 200. However, the potential for injury is substantially increased with each rise in g-max value. In general, a g-max of 130 or below is considered safe. A rating from 130 to 200 is suspect and a rating over 200 is considered too hard and unsafe for football playing surfaces.
For example, according to Southwest Recreational Industries, two synthetic football fields were installed by Field Turf Holdings, Inc. in 1999. These fields exhibited g-max values as high as 181 and 175, respectively, after only 13 months of use. Furthermore, these g-max values were obtained after and attempt to de-compact the fields. These values are very high and illustrate the problem one faces with particulate infills.
Accordingly, there is a need for machines that softens particulate infills and methods for softening particulate infills.